Weight Loss Knowledge

What Is Dehydration?


Although water is constantly lost throughout the day as we breathe, sweat, urinate and defecate, we can replenish our bodies by drinking water. The body can also divert water to where it is needed most if dehydration begins to occur. Most dehydration can be easily reversed by increasing fluid intake, but severe cases of dehydration require immediate medical attention.

What is Dehydration?

Dehydration occurs when you don’t have enough fluid in your body. Severe dehydration can lead to serious problems. If you suspect you (or someone else) is severely dehydrated, seek medical attention.

You become dehydrated when your body doesn’t have enough water to keep it working properly. This happens when your body loses too much fluid.

When your body has enough water to work properly, you are hydrated.

What are the Signs of Dehydration?

Symptoms of dehydration depend on whether the condition is mild or severe. The symptoms of dehydration may begin to appear before full dehydration occurs.

Symptoms of mild to moderate dehydration include:

  • fatigue
  • dry mouth
  • increased thirst
  • decreased urination
  • less tear production
  • dry skin
  • constipation
  • dizziness
  • lightheadedness
  • headache

In addition to the symptoms of mild dehydration, severe dehydration can lead to the following conditions:

  • excessive thirst
  • lack of sweat production
  • low blood pressure
  • rapid heart rate
  • rapid breathing
  • sunken eyes
  • shriveled skin
  • dark urine

Severe dehydration is a medical emergency. If you have any of these signs and symptoms, get medical help immediately.


It is normal to lose water from your body every day through sweating, breathing, urination and stool, and through tears and saliva (saliva). Usually, you replace lost fluids by drinking water and eating foods that contain water. If you lose too much water or don’t drink and eat enough, you can become dehydrated.

You may lose more water than usual when:

  • A fever
  • Diarrhea
  • Vomiting
  • Excessive sweating
  • Peeing more often (diabetes and some medications such as water pills – also called diuretics – can make you pee more often.)

You may not replace the water you lose because:

  • You’re busy and forget to drink enough.
  • You don’t realize you’re thirsty.
  • You don’t want to drink because you have a sore throat or mouth ulcer, or you have an upset stomach.

How is Dehydration Treated?

Treatment of dehydration depends on its severity. Children who are mildly dehydrated can get extra fluids at home. Children with more severe dehydration may need to be treated in an emergency room or hospital.

The treatment for mild dehydration is oral (mouth) rehydration. This usually involves giving oral rehydration solution (such as Pedialyte, Enfalyte, or store brands). It has the right amount of water, sugar and salt to help with dehydration. You can get it at a pharmacy or supermarket without a prescription. If you can’t buy oral rehydration solution, talk to your doctor. There are other fluids that can help with dehydration.

If your child has mild dehydration and your doctor says you can start treatment at home:

  • Give your child as many small sips of oral rehydration solution as possible, about 1 or 2 teaspoons (5 or 10 ml) every few minutes.
  • Infants can continue to breastfeed or take formula as long as they do not vomit repeatedly.
  • Older children also can have electrolyte ice pops.
  • Children can continue to eat their regular diet unless their doctor recommends a change. They may not want to eat at first, but as long as they’re drinking water, it’s okay if they don’t eat much solid food.
  • Do not give your infant plain water instead of oral rehydration solution. It does not have the right nutrients for a dehydrated infant.
  • Do not give sports drinks, sodas, or full-strength (undiluted) juices. They have too much sugar and can make some symptoms worse.
  • When your child starts to feel better and has a better appetite, you can reduce the oral rehydration solution and give them more of their usual food and drink.
  • Do not give medication for diarrhea or vomiting unless recommended by your doctor.

When to See Your GP

If your symptoms persist after drinking lots of fluids, or if you think your baby or toddler is dehydrated, see your GP.

If your GP suspects dehydration, you can have a blood test or urine test to check the balance of salts (sodium and potassium) in your body.

Contact your GP, out-of-hours service immediately if you have any of the following symptoms:

  • extreme thirst
  • feeling unusually tired (lethargic) or confused
  • not passing urine for eight hours
  • rapid heartbeat
  • dizziness when you stand up that doesn’t go away after a few seconds

You should also contact your GP if your baby has had 6 or more episodes of diarrhoea in the last 24 hours or 3 or more episodes of vomiting in the last 24 hours.

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